Jet flap controlling means



Dec. 2, 1969 M. KRETZ 3,481,560

JET FLAP CONTROLLING MEANS Filed June 15, 1967 1 5 Sheets-Sheet 1 Dec. 2, 1969 M. KRETZ 3, 1

' JET FLAP CONTROLLING mamas Filed June '15, 1967 5 Sheets-Sheet 2 JET FLAP CONTROLLING MEANS Filed June 13, 1967 5 shets sheet s 5 Shets-Sheet 4 M. KRETZ JET FLAP CONTROLLING MEANS Samar-" Dec. 2, 1969 Filed June 13, 1967 M. KRETZ v JET FLAP CONTROLLING MEANS Dec. 2, 1969 5 Sheets-Sheet Filed June 13, 1967 United States Patent 3,481,560 JET FLAP CONTROLLING MEANS Marcel Kretz, Paris, France, assignor to Giravions Dorand, Suresnes, France, a company of France Filed June 13, 1967, Ser. No. 645,771 Claims priority, application France, June 20, 1966, 66,166; May 12, 1967, 106,281 Int. Cl. B64c 3/42, 3/54 US. Cl. 244-42 Claims ABSTRACT OF THE DISCLOSURE The invention resides basically in jet flap control means in which an aerofoil having a jet slit trailing edge is provided with a flexible deflecting flap, and it comprises con-- trol means adapted by its geometry to differentiate between upward and downward flexure of such flap assembly to the required deflection of the jet stream; it also includes structures of flap adapted to accommodate such differential flexure.

SUMMARY OF INVENTION The jet flap control means, according to the invention, comprises positive control mechanism operative on the trailing edge of a flexible deflector flap element, in such a manner that differentiation occurs between upward and downward movement, so that the profile formed by flexure is adapted respectively to the aerodynamic requirements of positive deflection of the jet stream (when the flap acts like the positive face of a blade or vane and the working surface of the flap is concave) and the Coandalike deflection due to boundary-layer adherence to the surface (when the working surface is convex); it being established that curvature of different profile is required in the two respective axes. The invention includes constructional features aimed at the practical application of the control so provided.

More specifically, the present invention relates to a deflector arrangement for a fluid jet having mainly the object of modifying the direction of flow of fluid from a jet slitprovided at the trailing edge of an aerodynamic or hydrodynamic lifting or propulsive element with a view to controlling the forces on the element, for example an aeroplane wing or a helicopter blade of so-called blown type, the arrangement being of the kind also known as a jet flap. The arrangement according to the invention is, however, capable of numerous other applications, for example as a thrust-reverser of the jet of a jet-reaction device or a marine propulsive duct and analogously.

There are previously known deflector flaps of this kind which are constituted by a flexible sheet fixed by one of its edges at one of the lips of the slit, for example the lower lip, whichin its neutral position is in a plane parallel to the plane of symmetry of the jet and which by pneumatic or mechanical control means, is flexed in a curvature appropriate to the desired deflection of the jet. Realization of such control at present presents difliculties; a pneumatic control, for example, usually involves some kind of inflatable vessel as an actuator to cause the deformation of the flexible sheet, and it is not practicable with a single such control, to achieve jet deflections in the two opposed senses (up and down) in respect of the plane of symmetry of the jet.

Further, the profile taken up by the flexible sheet results in equilibrium between the control forces and forces exerted on the sheet by the jet itself, together with such other forces which vary according to the conditions of use, in respect of which there may not be a unique rela tion between the control and the deflection. Sheet-like 3,481,569 Patented Dec. 2, 1969 "ice flaps which are insensitive to external forces are diflicult to realize in practice, not only for the reason stated above, but also by reason of that fact that the phenomena to which the sheet is subjected may be very different according to whether the flap is flexed to deviate the jet upwards or downwards.

If the jet is to be deflected downwards to augment the lift afforded by the Wing of an aeroplane or a rotor blade of a helicopter, the flexible sheet being fixed to the lower lip of the jet slit is flexed in a manner to present a convex surface upwards, the jet stream following the profile of the sheet by the effect known as the Coanda effect; in order that there shall not be separation of the stream it is necessary that any radius of curvature of the flexed flap, which is subjected to positive pressure force on its under face and a lower pressure on its upper face, must not be less than a value approximately equal to ten times the height of the jet slit. When the sheet is flexed in a manner to present upward concavity so as to deviate the emerging jet upwards, the flexible sheet deviates the jet positively, in the manner of a blade or vane, and in this case the radius of curvature of the flexed sheet may be considerably less, for example equal to about twice the height of the jet slit.

The controlling and actuating means of deflector arrangement for the jet according to the present invention aims at meeting the requirements above indicated and takes account of the collective phenomena which arise in effecting the deflection of the jet; this arrangement is characterised by the fact that it comprises a positive control mechanism operative on the trailing edge of the flexible sheet and provided in such a manner as to impose on the sheet flexural deformations which are different according to which side of its neutral position (i.e. parallel to the plane of symmetry of the jet) it is flexed.

By way of example, there have been described below and represented by drawings examples of the invention and its basis.

FIGURE 1 is a diagram representing various possible flexural deformations of a flap-jet deflector in the form of a flexible sheet.

FIGURE 2 is a schematic view in sectional elevation of control mechanism applicable to achieve the flexures of FIGURE 1.

FIGURES 3, 4 and 5 show, by way of example, different constructions of the flexible sheet flap element itself.

FIGURES 6 and 7 represent schematically two ways of fixing of the flap element to its support and/ or its trailing edge.

FIGURES 8 and 9 respectively represent a sectional elevational and an underneath plan view of a flap with plural sheets, with its support and its trailing edge.

FIGURE 10 shows schematically an arrangement of a flap proposed for supersonic jets.

FIGURE 11 shows in elevation a flap akin to the scheme of FIGURE 10, with its control mechanism.

FIGURE 12 represents a variant of a feature shown in FIGURE 10.

As shown in FIGURE 1, the arrangement comprises a jet slit 1 on the lower edge or lip of which is fixed a flexible sheet 2 of a chord dimension L, which may be constituted, in the spanwise sense of the jet, by several separate elements each having its individual control. For the reasons explained above, should the jet be deflected downwards and the sheet 2 be flexed to present a convexity upwards (see lower part of FIGURE 1), the flexible sheet should have uniform curvature. If a is the angle of deflection of the jet, 1' the length of the vector radius, i.e., the straight line connecting the attachment of the leading edge of the sheet 2 to the trailing edge of the sheet 2, the best conditions to obtain laminar adhesion of the stream will be realized when the angle 12 of the radius is approximately equal to half the angle of deflection a, i.e.,

The variation of the vector radius as a function of the angle a changes according to a law of the 2nd degree capable of being expressed by the relation:

L 1 ka k being a parameter depending on the dimensional characteristics of the arrangement.

In the case of upward deflection, wherein the flexible sheet acts as a blade, it presents a surface which is concave upwards and it is subjected to the positive pressure of the jet. In this case, the radius of flexed curvature is not uniform, because due to the eifect of the effective pressure, part of the sheet 2 remains plane and the flexure increases in radius with the angle of deflection. It therefore results that the angle of the vector radius will vary more quickly as a function of the deflection angle than in the case of downward deflection, for preference following the relation:

1 b-tl whilst the variations of the length of the vector radius in upward deflection as a function of the angle a will be less than in the case of the downward deflection and will obey a cubic law given approximately by the relation:

.1 I 3 L l k a It should be noted that the above relations are empirical and are given by way of indication only of the magnitude of the important factors which may be applied in practice between the values of r and b as a function of the angle of deflection a in the concept of the asymmetric control of the trailing edge of the flexible flap element according to the invention.

FIGURE 2 represents a form of realization of such a control; on each lateral (spanwise) margin of the flexible sheet 2 or of an element thereof is mounted a mechanism comprising a first lever 3 hinged on a spindle 4 borne on the lower face of the aerofoil which is provided with the jet slit 1, the spindle 4 being entrained for rotation by the actuator of the control. At the rear extremity 5 of this lever 3 is articulated another lever 6 on the extremity of which is fixed the trailing edge of the flap element 2. At 7 of the lever 6, approximately in the middle of its length, is articulated a connecting link 8, the other (forward) end of which is pivoted at an axis 9 situated aft of the jet slit on a bracket 10 fixed to the aerofoil having the jet 1. The axis at 9 is situated approximately in the plane of symmetry of the jet stream.

The lengths of the levers 3, 6 and of the connecting link 8, as also the position of these parts in the neutral deflection position, are determined so as to obtain asymmetrical variations of curvature as shown in FIGURE 1. It is to be noted that with this mechanism for the approximately normal or neutral position of deflection substantially in the position represented in full line in FIGURE 2, the sheet 2 is flexed into this position. There have been shown in broken line two positions 2', 2", of the flexed sheet 2, respectively upwards and downwards, which show the geometric effects of the control mechanism above described. These are such as to provide the flexures of the sheet 2 in accordance with the diagram of FIGURE 1.

The jet flap which has been described affords jet deflection downwards extending to 90 and advantageously an upward deviation greater than 90 which makes it available as a thrust-reverser.

It is observed that the control mechanism allows use of the flap in non-powered flight; thus, in the case of engine failure or compressor failure and, therefore, absence of the jet, the arrangement may then function as a classical flap of high curvature. The flexures of the sheet 2 which may be desirable in these special circumstances not being the same as in the case of operation as a jet flap, the invention may provide a control actuation arrangement with double reduction.

As shown in FIGURE 3, the flexible flap may be constituted by several superimposed flexible sheets 11, 12, 13, for example, or by a combination of sheets, which may afford variable flexibility in the sense of depth and allowing more easy adaptation to the required laws of the profile formation. For example, as seen in FIGURE 4, the flap might be constituted by two principal laminae of sheet steel 14, 15 extending respectively from the lip of the jet slit to the trailing edge 16, between which are mounted auxiliary sheets which do not extend the full chord of the flap, for example, sheets 17, 18, 19 having different chords and only fixed at the leading edge of the flap, and further short-chord sheets such as 20 fixed to the trailing edge 16. As represented in FIGURE 5, the flap may be constituted by a single sheet 21 having a thickness tapering from the leading edge towards the trailing edge 16; this form is purely diagrammatic and in practice would require provision for the required flexibility.

Forms of realization of the multiple sheet flap described above and diagrammatically shown, aim at improving the flexible characteristics and are characterised by the fact that the flap is constituted by a sandwich structure comprising a plurality of thin metallic laminar sheets preferably of steel, separated one from the other by laminae of deformable elastic material such as rubber, stuck to the metallic sheet.

Such a flap is directly fixed by a single sheet, for ex-- ample, its upper sheet, both to the lip of the jet slit and to the profiled element forming the trailing edge operated by the control mechanism.

This disposition permits displacement of the extremities of the sheets, relative to their mutual support, and contributes to achieving the desired curvature of the flap during its flexures due to the fact that the bending of the individual sheets do not conflict.

In FIGURE 6, the flexible flap is constituted by two flexible steel sheets 31 and 32, separated by a layer of rubber 33, stuck to the two sheets. This assembly is fixed to the trailing edge part 34 in such manner that upon flexure of the flap relative movement may occur between the two sheets so as to take account of the differences of curvature between the external sheet situated on the convex side and the internal sheet situated on the concave side of the flap. To this eifect only the upper sheet 31 is directly fixed, for example, by soldering, to the part 34 around which it is folded so as to increase the area of soldering, the layer 33 of rubber terminating short of the part 34. The lower sheet 32 presents a rearward margin 35 folded back upon itself and fixed by adhesive through the intermediary of an elongated strip of rubber 36 on an edge 37 prolonging the lower part of the trailing edge part 34. In this manner, the rubber strip 36 and the folded back part 35 of the sheet take up the differences of flexure of the sheets 31 and 32 during their flexion. In the example of FIGURE 7, the flap is constituted by three superimposed sheets 38, 39 and 40, separated one from the other by two layers of rubber 41, 42. The upper sheet 38 is fixed with the part 34 in the same manner as in FIGURE 6, whilst the lower sheet 40 is fixed to the edge 37 of the part 34 also by adhesive with interposition of the rubber strip 36, but without being folded back upon itself. It is understood that these two methods of fixing may be combined, that of FIGURE 7 being, for example, used to fix the flap to the aerofoil, and that of FIGURE 6 for fixing to the part forming the trailing edge of the flap, notably when the lower sheet 40 does not fully extend over the chord of the flap.

FIGURES 8 and 9 represent a form of realization using such a combination of the two fixing methods described above. The deformable flap represented by these figures comprises three flexible steel sheets 43, 44 and 45, separated by layers of adherent rubber 46, 47, the lower sheet 45 not extending over the whole chord of the flap from the support 48 provided by the aerofoil.

This lower sheet 45 presents at its aft margin an outline of saw tooth pattern 49, 49', 49", either in the form of isosceles or equilateral triangles, this arrangement reinforcing the structure of the flap in the region of its attachment to the aerofoil and improving the progressive eflect of the curvature during flexure of the flap in both up and down senses.

The upper sheet 43 is fixed directly by soldering on the upper surface of the aerofoil attachment 48 and on the profiled trailing edge part 50, around which this sheet is folded. The two other sheets 44, 45 are inserted with the layers of rubber 46, 47 interposed between them in a longitudinal (spanwise) groove 51 provided in the attachment 48, a third sheet of rubber 52 being interposed between the lower sheet 45 and the lower face of the groove 51 of the attachment 48. The upper face of this groove is tapered as shown at 53 to facilitate the insertion of the flexible structure. As in FIGURE 6, the central sheet 44 is folded back upon itself lengthwise of its trailing margin at 54 and fixed by adhesive, with the interposition of a rubber strip 55, on the upper face of the edge 56 which is rigid with the part 50.

In FIGURES 1 to 5, the deformable flap was fixed directly to the lower lip of the jet slit, this disposition being usable for subsonic jets. In the case of supersonic jets, it is preferable to use the disposition represented in FIGURE 10, in which the deformable flap schematically represented at 57 is fixed to a support 58 forming an extension of the lower wall 59 of the jet slit 60. This support 58 presents a plane upper surface 61 inclined downwards with reference to the plane of symmetry X X of the jet in a manner to form a definite angle 62 with the lower wall 59 of the slit 60. FIGURE 11 represents in more detailed fashion, a realization according to FIG- URE The duct 60 is provided at each of its spanwise ends with a part 63 fixed by means of screws 64, 64' and extending by a support surface 65 having a plane upper face 66 inclined downwards so as to form a definite angle 67 with the 'slit wall at the lower lip of the jet slit, in the plane of exit of the latter, the flexible flap 57 being fixed on these plane faces in one of the ways described above. To the after extremities of the parts 63 is mounted a spanwise spindle 68 on which is articulated at each end of the slit a 'part 69 having the general form of a triangle, of which the after apex carries a spanwise pivot 70 on which is fixed a part 71 which is an end of the trailing edge (e.g. 34 or 50) of the flap. The lower apex of the part 69 carries a pivot 72 on which is articulated the after extremity 73 of connecting link 74 of which the forward extremity 75 may slide, by the action of an actuator control part not shown, in the transverse guide 76 provided in the lower part of the body of the aerofoil in which is situated the jet slit.

FIGURE 12 represents diagrammatically a variant of the structure shown in FIGURES l0 and 11, in which the part 77 with an upper plane face 78, on which is fixed the flexible flap element 79, is articulated on a spanwise aXis 80 to the aerofoil, below the jet slit 82. Connecting links 83, 84 act respectively on the rigid articulated support 77 and the trailing edge of the flexible flap 79.

Whatever actuating means is employed, whether hydraulic, pneumatic, electrical or mechanical, forming no part of the present invention, is arranged to operate (e.g. through 74 or 84) controllably and positively, and through a suflicient length of movement or stroke as to flex the flap up or down to the desired extent. As has been indicated, in the event of use being required as a conventional flap in the absence of a jet stream, the actuating mechanism may be adaptable to such purpose; for example, it may be disengaged and its duty taken over by hand actuation.

I claim:

1. A fluid jet deflecting device for an aerofoil, particularly applicable to fixed aircraft wings and to helicopter rotor blades, having a nozzle in the form of a slit at its trailing edge and at least one flexible deflector flap arranged along the lower lip of said slit and extending rearwardly therefrom, provided at each end of said flap with a control mechanism comprising a bracket fixed on the lower lip of the jet slit and projecting rearwardly therefrom, and a collapsible articulated quadrilateral of elongated shape of which one short rear side is formed by a connecting rod operatively connected by its rear end with the trailing edge of the flexible flap, of which one long side is formed by a control lever having its rear end articulated at the forward end of said connecting rod and its rear end movably arranged below the lower lip of said jet slit, a second short side of the collapsible quadrilateral being formed by a member having its rear end pivoted on a fixed axis arranged on the rear end of said bracket and having its forward end operatively connected with the first short side, whereas the fourth side of the collapsible quadrilateral is formed by the distance separating the rear end of said control lever and said fixed axis carrying said pivoted member, whereby unsymmetrical flexural deformations with respect to the plane of symmetry of the jet slit are imposed to the flexible flap according as it is flexed upwardly and downwardly either side of its neutral position.

2. A fluid jet deflecting device according to claim 1, wherein the collapsible articulated quadrilateral provided at each end of the flap comprises a first lever having its forward end hinged on an axis extending longitudinally of the lower part of the slit shaped nozzle, a second lever having its forward end articulated at the rear end of the first lever and its rear end connected to the trailing edge of the flexible flap, a bracket fixed on the lower lip of the slit and projecting rearwardly therefrom and a connecting link having its forward end pivoted on a fixed axis situated on said bracket, approximately in the plane of symmetry of the slit, and its rear end articulated on the second lever approximately in the middle of its length, actuating means being provided for rotating said first lever.

3. A fluid jet deflecting device according to claim 1, wherein both short sides of the collapsible quadrilateral are rigidly connected with one-another by their rear ends to form a triangular member articulated by their forward ends on the said fixed axis and on the control lever respectively.

4. A fluid jet deflecting device according to claim 1, wherein the collapsible articulated quadrilateral provided at each end of the flap comprises a member having the general shape of an elongated isosceles triangle having its axis of symmetry in a direction away from the jet slit and its apex forming the upper end of its basis pivoted on the said fixed axis arranged on the rear end of the said bracket fixed on the lower end of the jet slit, a transverse guide arranged in the lower part of the slit like nozzle, 'a control lever having its forward end slidably mounted in said guide and its rear end pivoted on the second apex of the triangular member forming the lower end of the basis thereof, whereas the third apex opposed to said basis is operatively connected to the trailing edge of the flexible 'flap.

5. A fluid jet deflecting device according to claim 1, wherein the collapsible articulated quadrilateral provided at each end of the flap comprises a member having the general shape of an elongated isosceles triangle having its axis of symmetry in a direction away from the jet slit and its apex forming the upper end of its basis pivoted on the said fixed axis arranged on the rear end of the said bracket fixed 0n the lower end of the jet slit, a transverse guide arranged in the lower part of the slit like nozzle, 21 control lever having its forward end slidably mounted in said guide and its rear end pivoted on the second apex of the triangular member forming the lower end of the basis thereof, whereas the third apex opposed to said basis is operatively connected to the trailing edge of the flexible flap, the said bracket having an upper plane surface inclined downwardly with respect to the plane of symmetry of the jet slit to form an obtuse angle with the upper surface of the lower lip References Cited FOREIGN PATENTS 1,239,330 7/1960 France.

MILTON BUCHLER, Primary Examiner J. L. FORMAN, Assistant Examiner 

